Auto merge of #77289 - TimDiekmann:alloc-ref-by-ref, r=Amanieu
Auto merge of #77289 - TimDiekmann:alloc-ref-by-ref, r=Amanieu

Change `AllocRef::by_ref` to take `&self` instead of `&mut self`

r? `@Amanieu`

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust